Answer
$\binom {n}{n}$ = 1
Work Step by Step
As $\binom {n}{r}$ = $\frac{n!}{r!(n - r)!}$
For any whole number $n$,
$\binom {n}{n}$ = $\frac{n!}{n!(n - n)!}$ = $\frac{1}{0!}$ = 1 $(\because$ for any whole number n, $0! = 1)$
Hence, for any whole number $n$, $\binom {n}{n}$ = 1
